Measurement and analysis of 233U from local thorium by using gamma spectrometry and DNCS methods

Abstract

The measurement and analysis of 233U from irradiated local thorium sample by gamma spectrometry and fission-induced delayed neutron counting system (DNCS) methods have been done. The sample was a small high purity local ThO2 produced from the extraction of monazite sand at our research center. The main goal of this experiment was to explore possibilities of 233U determination in the irradiated thorium for its future use in SAMOP reactor. Some ThO2 samples of 0.1 gram were irradiated at the Kartini reactor at average neutron flux of 1012 n cm-2s-1 and cooled down for 55 days before counted by gamma spectrometry where 233U determined indirectly by gamma peak counting of 233Pa. The samples then re-irradiated to determine 233U by using DNCS method. The analysis result both by using gamma spectrometry and DNC methods were 10.10 ± 0.96 μg and 17.22 ± 1.85 μg of 233U in average. Of the two gamma spectrometry and DNCS methods both provided results in somewhat relatively good agreement with the calculated amounts of 233U using ORIGEN2 computer code i.e. 14.3 μg. The detection limit of DNCS and the efficiency of detection system measured are 0.006 μg and 6.39 ± 0.07% respectively, and the efficiency of gamma spectrometry system is 17.8%.